I'm aware it could be done with a new #(assoc-set! ... ) using default values.

I was wrong: This doesn't work! Sorry!

Yes, if you set the 'padding value like this, it will apply to all tenuto marks in your file. If you reset it to another value, it will change the 'padding values of every tenuto to the new value. So, unfortunately, it's not like using \override and \revert.

You could do something like this to "revert" to Lily's default:

\version "2.14.2"

#(assoc-set! (assoc-ref default-script-alist "tenuto") 'padding 0.75)

{

c''1_-

\once \override Script #'padding = #0.2

c''1_-

c''1_-

}

I was hoping to be able to set 'padding to a procedure. But 'padding doesn't respond if set that way, as I noted on an earlier email of this thread. I wonder if I'm doing something wrong here -- can 'padding be set to a procedure somehow?